Production of Engineered Biochars for Phosphate Removal from Waste Lignocellulosic Materials: First, Second, and Third Generation Engineered Products

This report evaluates three generations of engineered biochar made from anaerobically digested dairy fiber, urban wood residuals, wheat straw, compost overs, and other lignocellulosic materials. Researchers used carbon-dioxide activation, nitrogen doping, and combined metal-nitrogen doping to improve biochar’s ability to capture phosphate from liquid waste and hydrogen sulfide from biogas. Carbon-dioxide-activated dairy-fiber biochar removed both contaminants, while one-step nitrogen doping substantially increased phosphate adsorption. Magnesium-nitrogen doping produced the strongest phosphate adsorption, reaching 335 milligrams per gram in cellulose-derived biochar. Tests also found that raw particle-board biochar increased the water-holding capacity of sandy soil, although nitrogen doping provided little additional benefit. These engineered biochars could help biorefineries recover nutrients, clean biogas and wastewater, and create valuable soil amendments. Further research is needed to determine whether captured phosphate remains available to plants.